Superconductors, whether polymeric or ceramic, are innovative materials capable of intrinsic properties such as levitation and conduction of electrical currents without resistance. These properties are due to the electrons being grouped in Cooper pairs, behaving as bosons.
Typically, mixed metal oxide materials exhibit high-temperature superconductivity as illustrated for example, in U.S. Pat. No. 6,794,339, the entire contents of which is incorporated herein by reference. The rare-earth-metal-alkaline-earth-metal-copper oxide superconductor materials are generally of the formula RBa2Cu3O7-x. However, the ceramic nature of the superconductor materials pose a number of problems for the manufacture of high critical temperature (Tc) superconducting shaped products such as magnetic levitation components and magnetic shielding devices. Because the mixed oxide superconducting materials are susceptible to degradation by moisture and chemicals such as reducing agents, their use in various applications are limited. In addition, conventional ceramic superconductors are difficult to be molded, easily breakable and thus, difficult to be molded or folded in different forms such as tubes, cylinders, cubes, electric cables and wires, toroids (for use in transformers), train tracks, nucleus for industrial performers, etc.
In contrast, magnesium diboride (MgB2) is a simple, inexpensive ionic binary compound superconducting material. MgB2 has a Tc of 39 K (−234° C.; −389° F.), the highest amongst conventional superconductors, as shown for example, in U.S. Pat. No. 7,338,921, the entire contents of which is incorporated herein by reference. Conventionally, MgB2 is a phonon-mediated superconductor, its electronic structure is such that there exists two types of electrons at the Fermi level with widely differing behaviors, one of them (sigma-bonding) being much more strongly superconducting than the other (pi-bonding). This is at odds with usual theories of phonon-mediated superconductivity which assume that all electrons behave in the same manner.
MgB2 typically only shows competitive properties at relatively low magnetic field values which are useful for biomedical applications such as conductors for MRI magnets. However, the effort and success in improving MgB2 in high magnetic fields remains desirable. Therefore, enhancing the critical current of MgB2 in high magnetic fields such as tracks for levitation trains, tubes and wires, remains one of the main goals to be pursued through the control and manipulation of the structure at a nanometer level to increase flux pinning.
In addition, methods which provide superconductor composite materials that facilitate the cost effective manufacture of high Tc superconducting products of various shapes also remain desirable.